Question: A circle has a sector with area $\dfrac{39}{10}\pi$ and central angle $156^\circ$. What is the area of the circle? ${9\pi}$ $\color{#9D38BD}{156^\circ}$ ${\dfrac{39}{10}\pi}$
Explanation: The ratio between the sector's central angle $\theta$ and $360^\circ$ is equal to the ratio between the sector's area, $A_s$ , and the whole circle's area, $A_c$ $\dfrac{\theta}{360^\circ} = \dfrac{A_s}{A_c}$ $\dfrac{156^\circ}{360^\circ} = \dfrac{39}{10}\pi \div A_c$ $\dfrac{13}{30} = \dfrac{39}{10}\pi \div A_c$ $A_c \times \dfrac{13}{30} = \dfrac{39}{10}\pi$ $A_c = \dfrac{39}{10}\pi \times \dfrac{30}{13}$ $A_c = 9\pi$